Background: We recently encountered a case of a midline upper lip sinus, one of the rarest congenital lip sinuses. Several embryological hypotheses have been proposed regarding the etiology of this rare disease, but it remains obscure. Methods: We reviewed all cases of upper lip sinus reported in the English language through 2011, and classified them into three types according to accompanying anomalies and the site of the fistula. Results: Twenty-eight studies involving 31 cases were reviewed and classified. A type I sinus was a midline sinus without accompanying anomalies. There were 13 such cases, with a female predilection. Type II sinuses were midline sinuses with accompanying anomalies, and there were nine such cases. Type III sinuses were lateral sinuses with or without accompanying anomalies; there were nine cases. Conclusions: Our classification scheme is not only convenient for clinical application, but also reflects the embryological process responsible for congenital lip sinuses.
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